The design and development of new materials is required to meet the challenge of sustainable and environmental friendly energy production and storage. Computer simulations in the form of atomic-scale electronic structure calculations can be expected to play an important role in this, as demonstrated since the early part of this century. Most of such calculations are carried out in the framework of Density Functional Theory (DFT) (Hohenberg and Kohn 1964; Kohn and Sham 1965), which demonstrates a good compromise between computational speed and accuracy of the calculations. The ever-increasing computational power makes it possible today to study fairly complex structures with several hundreds or even thousands of atoms. A few examples of materials design studies include the search for novel materials for carbon capture and storage (Lin et al. 2012), batteries (Ceder et al. 1998), stable binary and ternary alloys (Curtarolo et al. 2012), transparent conductors (Hautier et al. 2013), dye-sensitized solar cells (Ørnsø et al. 2013), photovoltaics (d’Avezac et al. 2012; Hachmann et al. 2011), and water splitting materials (Castelli et al. 2012a, 2012b; Wu et al. 2013).